Hannibal Lecter is arguably the world’s most famous psychopath. I know — he’s not real. Still, the anti-hero of “The Silence of the Lambs” embodies the chilling constellation of traits generally associated with this rare mental disorder. A highly-intelligent physician and psychiatrist, Lecter is superficially charming, even urbane — at least when he’s not cannibalizing his innocent victims. He is rarely emotional, and despite the brutality of his crimes, he shows absolutely no evidence of empathy or a guilty conscience.

That’s what makes psychopaths so mysterious and incomprehensible — the lack of normal human feeling. How could somebody’s child develop into that kind of merciless automaton? What did Hannibal Lecter’s inner life feel like as he was growing up?

One leading idea is that this psychopathic derangement is linked to childhood temperament, specifically fearlessness, which lays the groundwork for the development of full-blown psychopathic disorder in adulthood. There is evidence to support this notion: Psychopaths have great difficulty learning about pain — learning to avoid electrical shocks and loud noises, for example — and their ability to recognize fearful faces is also impaired. Perhaps most notably, psychopaths don’t respond normally to fear-inducing punishments — making it very hard for parents and others to teach them right and wrong.